K R Puram, Bangalore - 36

Cambridge Institute of Technology, Bangalore

Department of Mechanical Engineering

Certificate

This is to certify that MrKARTHIK KUMAR. Hof VIII semester Mechanical Engineering, USN 1CD12ME038haspresented a technical seminar on the topic “i-VTEC” on 16/03/2016as prescribed by VTU for BE course.

The detailed original report of the technical seminar is submitted to the department for evaluation.

Signature of candidate with date

Signature of Internal guide with date Signature of Coordinator with date

Marks awarded

Signature of HOD with date

Visvesvaraya Technological University, Belgaum

Technical Seminar

i-VTEC

Presented

KARTHIK KUMAR. H

(1CD12ME038)

Under the Guidance of

SUHAS. U

Assistant Professor

(2014-15)

Department of Mechanical Engineering

Cambridge Institute of Technology

K R Puram, Bangalore-36

2015-16

I-VTEC REPORT

ABSTRACT

The most important challenge facing car manufacturers today is to offer vehicles that deliver excellent fuel efficiency and superb performance while maintaining cleaner emissions and driving comfort. This paper deals with i-VTEC(intelligent-Variable valve Timing and lift Electronic Control) engine technology which is one of the advanced technology in the IC engine. i-VTEC is the new trend in Honda’s latest large capacity four cylinder petrol engine family. The name is derived from ‘intelligent’ combustion control technologies that match outstanding fuel economy, cleaner emissions and reduced weight with high output and greatly improved torque characteristics in all speed range. The design cleverly combines the highly renowned VTEC system - which varies the timing and amount of lift of the valves - with Variable Timing Control. VTC is able to advance and retard inlet valve opening by altering the phasing of the inlet camshaft to best match the engine load at any given moment. The two systems work in concern under the close control of the engine management system delivering improved cylinder charging and combustion efficiency, reduced intake resistance, and improved exhaust gas recirculation among the benefits. i-VTEC technology offers tremendous flexibility since it is able to fully maximize engine potential over its complete range of operation. In short Honda's i-VTEC technology gives us the best in vehicle performance.

TABLE OF CONTENTS

 INTRODUCTION

 NEED OF i-VTEC TECHNOLOGY

 HISTORY

 i-VTEC MECHANISM

 i-VTEC SYSTEM LAYOUT

 FUTURE OF i-VTEC

 INTELLIGENT-VTEC THE NEXT GENERATION

 CURRENT STATE OF i-VTEC

 TYPES OF i-VTEC ENGINES

 i-VTEC IMPLEMENTATION

 APPLICATION

 FUTURE TRENDS

 ADVANTAGES

 DISADVANTAGES

 CONCLUSION

 REFERENCES

INTRODUCTION

1.1 i- VTEC

Honda i-VTEC (intelligent-VTEC) has VTC continuously variable timing of camshaft phasing on the intake camshaft of DOHC VTEC engines. The technology first appeared on Honda's K-series four-cylinder engine family in 2001 (2002 in the U.S.). In the United States, the technology debuted on the 2002 Honda CR-V.

VTC controls of valve lift and valve duration are still limited to distinct low- and high-RPM profiles, but the intake camshaft is now capable of advancing between 25 and 50 degrees, depending upon engine configuration. Phasing is implemented by a computer-controlled, oil-driven adjustable cam gear. Both engine load and RPM affect VTC. The intake phase varies from fully retarded at idle to somewhat advanced at full throttle and low RPM. The effect is further optimization of torque output, especially at low and midrange RPM. There are two types of i-VTEC K series engines which are explained in the next paragraph.

1.2 K-series

The K-Series motors have two different types of i-VTEC systems implemented. The first is for the performance motors like in the RSX Type S or the Civic Si and the other is for economy motors found in the CR-V or Accord. The performance i-VTEC system is basically the same as the DOHC VTEC system of the B16A's; both intake and exhaust have 3 cam lobes per cylinder. However the valve train has the added benefit of roller rockers and continuously variable intake cam timing. Performance i-VTEC is a combination of conventional DOHC VTEC with VTC.

The economy i-VTEC is more like the SOHC VTEC-E in that the intake cam has only two lobes, one very small and one larger, as well as no VTEC on the exhaust cam. The two types of motor are easily distinguishable by the factory rated power output: the performance motors make around 200 hp (150 kW) or more in stock form and the economy motors do not make much more than 160 hp (120 kW) from the factory.

NEED OF i-VTEC TECHNOLOGY

In this modern world of car, everybody wants great mileage in his/her car, so to produce such a car which has mileage and great power the i-VTEC technology is used in engines.

As we know the price of fuel is increasing day by day, hence the proper fuel utilization in engine is very important. As in other cars, power with mileage is not possible but due to this technology it is possible to get both in one car.

HISTORY

VTEC, the original Honda variable valve control system, originated from REV (Revolution-modulated valve control) introduced on the CBR400 in 1983 known as HYPER VTEC. In the regular four-stroke automobile engine, the intake and exhaust valves are actuated by lobes on a camshaft. The shape of the lobes determines the timing, lift and duration of each valve. Timing refers to an angle measurement of when a valve is opened or closed with respect to the piston position (BTDC or ATDC). Lift refers to how much the valve is opened. Duration refers to how long the valve is kept open. Due to the behaviour of the working fluid (air and fuel mixture) before and after combustion, which have physical limitations on their flow, as well as their interaction with the ignition spark, the optimal valve timing, lift and duration settings under low RPM engine operations are very different from those under high RPM. Optimal low RPM valve timing, lift and duration settings would result in insufficient filling of the cylinder with fuel and air at high RPM, thus greatly limiting engine power output. Conversely, optimal high RPM valve timing, lift and duration settings would result in very rough low RPM operation and difficult idling. The ideal engine would have fully variable valve timing, lift and duration, in which the valves would always open at exactly the right point, lift high enough and stay open just the right amount of time for the engine speed in use.

i-VTEC MECHANISM

4.1 i-VTEC

The latest and most sophisticated VTEC development is i-VTEC ("intelligent" VTEC), which combines features of all the various previous VTEC systems for even greater power band width and cleaner emissions. With the latest i-VTEC setup, at low rpm the timing of the intake valves is now staggered and their lift is asymmetric, which creates a swirl effect within the combustion chambers. At high rpm, the VTEC transitions as previously into a high-lift, long-duration cam profile. The i-VTEC system utilizes Honda's proprietary VTEC system and adds VTC (Variable Timing Control), which allows for dynamic/continuous intake valve timing and overlap control. The demanding aspects of fuel economy, ample torque, and clean emissions can all be controlled and provided at a higher level with VTEC (intake valve timing and lift control) and VTC (valve overlap control) combined. Fig.4.1

The i stands for intelligent: i-VTEC is intelligent-VTEC. Honda introduced many new innovations in i-VTEC, but the most significant one is the addition of a variable valve opening overlap mechanism to the VTEC system. Named VTC for Variable Timing Control, the current (initial) implementation is on the intake camshaft and allows the valve opening overlap between the intake and exhaust valves to be continuously varied during engine operation. This allows for a further refinement to the power delivery characteristics of VTEC, permitting fine-tuning of the mid-band power delivery of the engine.

Fig. 4.1

4.2 VTEC ENGINE:

VTEC (standing for Variable valve Timing and lift Electronic Control) does Honda Motor Co., Ltd. develop a system. The principle of the VTEC system is to optimize the amount of air-fuel charge entering, and the amount of exhaust gas leaving, the cylinders over the complete range of engine speed to provide good top-end output together with low and mid-range flexibility. VTEC system is a simple and fairly elegant method of endowing the engine with multiple camshaft profiles optimized for low and high RPM operations. Instead of only one cam lobe actuating each valve, there are two - one optimized for low RPM smoothness and one to maximize high RPM power output. Switching between the two cam lobes is controlled by the engine's management computer. As the engine speed is increased, more air/fuel mixture needs to be "inhaled" and "exhaled" by the engine. Thus to sustain high engine speeds, the intake and exhaust valves needs to open nice and wide. As engine RPM increases, a locking pin is pushed by oil pressure to bind the high RPM cam follower for operation. From this point on, the valve opens and closes according to the high-speed profile, which opens the valve further and for a longer time.

4.3 BASIC V-TEC MECHANISM

The basic mechanism used by the VTEC technology is a simple hydraulically actuated pin. This pin is hydraulically pushed horizontally to link up adjacent rocker arms. A spring mechanism is used to return the pin back to its original position.

Fig 4.2

To start on the basic principle, examine the simple diagram below. It comprises a camshaft with two cam- lobes side-by-side. These lobes drive two side-by-side valve rocker arms.

The two cam/rocker pairs operate independently of each other. One of the two cam-lobes are intentionally drawn to be different. The one on the left has a "wilder" profile, it will open its valve earlier, open it more, and close it later, compared to the one on the right. Under normal operation, each pair of cam- lobe/rocker-arm assembly will work independently of each other.

VTEC uses the pin actuation mechanism to link the mild-cam rocker arm to the wild-cam rocker arm. This effectively makes the two rocker arms operate as one. This "composite" rocker arm(s) now clearly follows the wild-cam profile of the left rocker arm. This in essence is the basic working principle of all of Honda's VTEC engines.

4.4 DIFFERENT VARIANTS OF V-TEC

Fig. 4.3

VARIABLE TIMING CONTROL (VTC)

VTC operating principle is basically that of the generic variable valve timing implementation (this generic implementation is also used by Toyota in their VVT-i and BMW in their VANOS/double-VANOS system). The generic variable valve timing implementation makes use of a mechanism attached between the cam sprocket and the camshaft. This mechanism has a helical gear link to the sprocket and can be moved relative the sprocket via hydraulic means. When moved, the helical gearing effectively rotates the gear in relation to the sprocket and thus the camshaft as well.

Fig 5.1

5.1 VTC principle

The drawing above serves to illustrate the basic operating principle of VTC (and generic variable valve timing). A labels the cam sprocket (or cam gear) which the timing belt drives. Normally the camshaft is bolted directly to the sprocket. However in VTC, an intermediate gear is used to connect the sprocket to the camshaft. This gear, labelled B has helical gears on its outside. As shown in the drawing, this gear links to the main sprocket which has matching helical gears on the inside. The camshaft, labelled C attaches to the intermediate gear. The supplementary diagram on the right shows what happens when we move the intermediate gear along its holder in the cam sprocket. Because of the interlinking helical gears, the intermediate gear will rotate along its axis if moved. Now, since the camshaft is attached to this gear, the camshaft will rotate on its axis too. What we have achieved now is that we have moved the relative alignment between the camshaft and the driving cam-sprocket - we have changed the cam timing!

Fig. 5.2

5.2. i- VTEC DOHC (Double Overhead Cam)

The last evolution of Honda’s VTEC system was back in 1995 where they introduced the now-famous 3- stage VTEC system. The 3-stage VTEC was then designed for an optimum balance of super fuel economy and high power with drivability. For the next 5 years, Honda still used the regular DOHC VTEC system for their top power models, from the B16B right up to the F20C in the S2000. Now Honda has announced the next evolution of their legendary VTEC system, the i-VTEC.

The “I“ stands for intelligent: i-VTEC is intelligent-VTEC. Honda introduced many new innovations in i- VTEC, but the most significant one is the addition of a variable valve opening overlap mechanism to the VTEC system. Named VTC for Variable Timing Control, the current (initial) implementation is on the intake camshaft and allows the valve opening overlap between the intake and exhaust valves to be continuously varied during engine operation. This allows for a further refinement to the power delivery characteristics of VTEC, permitting fine-tuning of the mid-band power delivery of the engine.

5.3 Variable Timing Control Operating Principle

Honda’s VTC operating principle is basically that of the generic variable valve timing implementation (this generic implementation is also used by Toyota in their VVT-i and BMW in their VANOS/double-VANOS system). The generic variable valve timing implementation makes use of a mechanism attached between the cam sprocket and the camshaft. This mechanism has a helical gear link to the sprocket and can be moved relative the sprocket via hydraulic means. When moved, the helical gearing effectively rotates the gear in relation to the sprocket and thus the camshaft as well.

Fig 5.3

The supplementary diagram on the right shows what happens when we move the intermediate gear along its holder in the cam sprocket. Because of the interlinking helical gears, the intermediate gear will rotate along its axis if moved. Now, since the camshaft is attached to this gear, the camshaft will rotate on its axis too. What we have achieved now is that we have moved the relative alignment between the camshaft and the driving cam-sprocket - we have changed the cam timing!

VTC and other implementations of generic variable valve timing can only change the relative alignment between the camshaft and its driving sprocket. What this effectively does is to change the relative timing between the intakes and exhaust cams and thus their valve opening cycles or the intake and exhaust valve opening overlaps. Note that no other valve timing parameters, e.g. amount of valve lift or absolute valve opening duration can be varied. The only thing that VTC varies is the valve opening overlaps. VTEC is able to vary all valve timing parameters but current implementations do so in two or three distinct stages (or profiles). Adding VTC allows the valve opening overlaps to be continuously varied and thus enables the power delivery from the standard VTEC system to be further fine-tuned. The greatest impact will be to the mid-band power delivery of the engine. Most importantly, VTC (and generic valve timing systems) will not replace VTEC but enhance its effectiveness.

5.4 i-VTEC SYSTEM LAYOUT

Fig 5.3

5.5 i-VTEC SYSTEM

Diagram explains the layout of the various components implementing i-VTEC. I have intentionally edited the original diagram very slightly - the lines identifying the VTC components are rather faint and their orientation confusing. I have overlaid them with red lines. They identify the VTC actuator as well as the oil pressure solenoid valve, both attached to the intake camshaft's sprocket. The VTC cam sensor is required by the ECU to determine the current timing of the intake camshaft. The VTEC mechanism on the intake cam remains essentially the same as those in the current DOHC VTEC engines except for an implementation of VTEC-E for the 'mild' cam.